"This SAE Recommended Practice is intended as a guide toward standard practice but may be subject to frequent change to keep pace with experience and technical advances. Purpose The purpose of this document is to provide dimensions of clearance envelopes for various types of six-bolt regular-duty@ eight-bolt heavy-duty@ and side- and rear-mounted truck transmission power takeoffs. These envelopes are applicable to the clearance required immediately adjacent to the power takeoff openings on truck transmissions. Clearance envelopes are provided for the purpose of documenting current practice. It must be recognized that many current designs do not provide these clearances in all orientations and variations. New transmission and power takeoff designs should attempt to adhere to these envelopes where practical@ but they should not be construed to be design restrictive; ultimately@ the actual power takeoff clearance must be established for each application. In order to provide realistic envelope sizes@ there are seven basic ""types"" of side-mounted P.T.O. envelopes and rear-mounted envelopes. All envelopes shown are basic and can be reversed for output to the front or rear of the vehicle. On Types II@ III@ IV@ and VI@ output shaft locations can additionally be reversed from that shown to the opposite side of the P.T.O. opening centerline. Driveline envelopes@ front or rear@ above or below centerline of opening as required@ must be a cylinder of the minimum diameter shown and fall within the 15 degree maximum half-cone extending vertically up and down and horizontally outward from the driveline cone apex@ for a distance equivalent to that required to bring the P.T.O. driveline beyond points of interference so that auxiliary equipment can be driven. Clearance should be provided on six-bolt openings on mechanical transmissions for Types I@ II@ and III with Types I and II being a minimum requirement. Clearance should be provided on automatic transmissions for Types IV and VI depending on six- or eight-bolt P.T.O. openings. Mechanical transmissions with eight-bolt openings should have Type V and VI clearances provided. Direct mount hydraulic pump clearance envelopes are included as an option@ and are commonly used with Types II@ IV@ and VI P.T.O. envelopes. If pump clearance is restricted it should be evaluated on a specific basis. If specific pump sizes are not available. Direct mount pump clearance envelopes should be used."